Telephone system



Oct. 27, 92 1,559,291

- w. P. ALBERT v TELEPHONE SX'STEQI Filed 001;. 1923 Q 5 Sheets Sheet 1gill Wren/0n h d/fer. PA/bfi,

W. P. ALBERT TELEPHONE SYSTEM Filed Och- 1923 s sheets sheei 2 1,559,297w. P. ALBERT v TELEPHONE SYSTEM Filed Oct. 6, 1923 5 Sheets-Sheet 5 Oct.27, 1925. 1,559,297 W. P. ALBERT TELEPHONE SYSTEM Filed Oct. 2 1923 5Sheets-Sheet 4 Wren/or? M/farP/l/ben,

Oct. 27,1925. 1,559,297

W. P. ALBERT TELEPHONE SYSTEM Filed Oct. 1923 5 sheets sheet 5 MM! H ml/MA/fk Patented Get. 27, 1925.

UNITED STATES PATENT OFFICE.

W LTER I ALBERT, r EAST 'Q RANGE. N W'JEnsEY, Assmnon r WESTERN ELEG-Te-Ic CQMPANY, INCORPORATED, or X. A rone 11 N W YORK.

TELEPHONE SYSTEM.

Application filed October 26, 1823. i .S eria1.No. 67.0,820.

To aZZ 107mm it may concern: 7

Be itknown that I, l VALTER P. ALBERT, a citizen of the United States.resfding at East Orange, in. the county of Essex and State of New.Jersey. have invented certain new and useful Improvements in TelephoneSystems, of which the following is a full, clear, concise, and. exactdescription.

This invention relates to .telephone systems and more particularly :toprivate branch exchange systems of the machine switching type.

lVFth the general trend of telephony toward mechanical operation, it isnecessary that private loranch exchanges be equipped with apparatusnecessary in completing connections between machine switchingsubscribers, and in extending calls to other machine switch'ngexchanges.

It is an object of this invention to furnish a private branch exchangeattendant with the min'mum amount of equipment necessary in completingthe various types of connections common to .a private branch exchange. i

This object is attained in accordance w'th 'a feature of the inventionby the provision of a cord circuit and an associated atten-dants dialand telephone circuit. wherein a plurality of keys are prOvEded, whichmay be operated singly or collectively, to connect the dialing equipmentwith either the front or rear end of thecord circuit. as the connect'onto be established may require. 7

Another feature of the invention resides in a circuit arrangementwherein the operation of a listening-key n a cord circuit .to connectthe attcndant s telephone set thereto. renders the operation of a secondlisteni k hey ineffective to connect the telephone set a second cor-dcircuit until the first hey is restored. By this arrangement, anattendant is unable to listen in on more than one connection at a time.

A further feature of the invention resides i a trunk circuit whereinmeans are provided for preventing the false operation of the trunksignal when the private branch exchange attendant disconnects her cordcircuit from the trunk.

A. still further feature of the inv nt on resides in anv arrangement forp e e ting the false operation of a tie linepulsing relaywhen a call,incomingfrom a central off ce exehan is' extended ove the t e line byway .of the attendants cord circuit. fleeting this feature, a relay thetie line ircuit. s-pro i e whi h cosh-' 1s th connection ott e p l ingre ay o h ja k o the tie linen When'the'fr nt en 'of the cord,employedin complet ng a. connectiom is connectedto a cen ral .of ce t unand the rea end to tie line and th tel ins and iiia i key actuated, t ecentra cfiice b ttery Wifi b connected straigh through he cord cuit tothe jack of the tie line. When the throughdia-ling key is actuated, apair of relays in the ope o dia and telep one circuit oper e to disconnet the ent a .Q fifi battery from the tle'line, connecta holding bridgacro s th en al f i runk and then cause the operation of the abovementioned tie line relay which onne t th tie line pulsing relay to thejack of the tie line.

The above and other-objects'of this invention will be readily understoodfrom the following detailed description made with referenceto theaccompanying drawings, in which Fig. lshows a local P. B. X. machineswitching subscr lbers line and the automatic equipment necessary forsignaling an attendant at the privatebranch exchange; Fig. 2shows B.attendants cord circuit involving features of this invention; Fig. 3showsthe attendants dial-and talking equip ment which functions with thecord circuit shown in Fig. 2:, Fig. 4 showsa centralotfi c'e trunkoutgoing from .the private branch exchange, and the automatic equipmentnecessary in establishing a call therefrom to a machine switchingsubscribers line; and Fig. 5 shows a portion of a.tie line, by means ofwhich a connection may be established from one private branch exchangeto another private branch exchange.

c ra. from P. n. 1 010.0. aitendcmt dialing/ ewer from end).

Assuming that a machine switching subscriber at station A desires toconverse with a subscriber at station E, whose line terminates in adistant machine switching exchange, the operation is as follows:

Upon removal of the receiver at station A, an operating circuit for slowrelease relay, 100 is established, which may be traced from battery,winding of relay 100, back contact and inner left-hand armature of relay101, the subscribers line loop to ground, over the outer left-handarmature and back contact of relay 101. Relay 100 establishes an obviouscircuit for the low resistance righthand winding of relay 101, which inoperat ing, actuates the line switch plunger 102. The plunger 102 causesthe tip, ring and sleeve conductors of the line A to be connected tocorresponding brushes of a selector switch 5 of the step by step typewell known in the art.

The subscriber then actuates the dial associated with the line A, inorder to send out a code of impulses, such as 9, which digit, whendialed, causes the selector S to be operated to select a group of trunksand automatically hunt for and connect the brushes to an idle trunkleading to the private branch exchange attendants position.

When an idle trunk is reached a ground, associated with the terminal108, causes the left-hand high resistance winding of relay 101 to becomeenergized in an obvious circuit. Relay 101 by pulling up its outer lefthand arn'iature, and plunger 102, and by causing the connection ofground 103 to the line, as just explained, serves to connect ground tothe respective sleeve terminals of jack J and connector C which areniutiple terminals of the calling line. This ground, causes the line Ato test busy on all incoming calls.

{elay 101 also opens the operating circuit for slow release relay 100,which. after an interval, releases its armature, thereby opening thecircuit for the riglit hand winding of relay 101. The slow releasecharacteristic of relay 100 enables relay 101 to remain operated overits right-hand winding until the ground from the selector circuitcompletes the energizing circuit for the lefthand winding. The lineswitch plunger 102 is accordiu 7 held actuated as long as the connectionis maintained.

Vihen the tip and ring tern'iinals, 10st and 105, of the idle trunk F1are connected to corresponding r-rig'iers of the selector switch 5%.relay 100 (moi-ates over the subscribers line loop, caui-ing the lamp107 to be illuminated as an indication to the private branch exchangeattendant that there is a call awaiting her attention. The attendantthen inserts the rear end plug 200 of the cord circuit K into the trunkjack J corresponding to the illuminated lamp 107. This operation closesthe local jack contacts 109, causing cut-ofi relay 108 to opcrate in anobvious circuit, whereupon relay 100 releases and lamp 107 isextinguished'.

Answering supervisory relay 201 in the attendants cord circuit, nowoperates in a circuit extending from battery, armature 223 and backcontact of relay 202, lower winding of retardation coil 2033, contact250 of key 210, winding of relay 201, lower normal contacts of ringingkey 205, ring contacts of plug 200 and jack J, terminal 105 and thecorresponding brush contacts 110 of the line switch, over thesubscribers line loop, contacts 111 of the line switch, brush andterminal 10%, tip contacts of jack J and plug 200, upper normalcont-acts of ringing key 205, contacts 228 of key 210, upper winding ofretardation coil 203 to ground over the inner left-hand armature andback contact of relay 202. Relay 201 in operating, prevents lamp 206from illuminating at this time and prepares a circuit for relay 207. Thecalling supervisory lamp 208, however, illuminates in a circuitextending from grounded battery, lamp 208, back contact and armature 221of relay 202, back contact and armature of calling supervisory relay209, sleeve contacts of plug 200 and jack J, to ground over therighthand armature and front contact of relay 108.

The attendant now actuates the talk and dial key 204, to connect herheadset with the calling line. At the contacts 211 of key 204, a circuitfor relay 212 is established, which may be traced from grounded battery,lower winding of relay 212, key contacts 211, conductor 224 to groundover the back contact and upper armature of relay 325. Relay 212, at itsinner upper armature, establishes an energizing circuit for relay 213 byway of the contacts 214 of key 20 1. Relay 213, at its inner upperarmature, causes relay 325 to operate in a circuit extending fromgrounded battery tl'irough the winding of relav 325, conductor 230,winding of relay 212, to ground over the front contact and inner upperarmature of relay 213. This circuit acts as a holding circuit for relay212 after the circuit through its energizing winding is opened by theoperation of common relay 325, so that it is now impossible to energizeanother relay, similar to relay 212, associated with another cordcircuit, should its associated talk and dial key 204 be operated. It is,therefore, apparent that the attendant cannot listen-in on more than oneconnection at a time.

Relay 325 at its lower armature and front contact, connects theleft-hand windings of repeating coil 341 across the right-hand windingsof repeating coil 365 by way of the outer right-hand armature and backcontact of relay 339 and condenser 360. The

operators headset 332 is now bridged. acrossthe rear; end. of the cordcircuit since relaya212,/in. attracting its: armatures 215.

and 218, relay 212 connects the retardation coil 351 across the frontend; of the .cord by way of conductors 253 and 254- and the outerarmatures and back contacts of relay 352' and the normalmake-before-break contacts :of relay 350.: e

The attendant now requests the nature of theicall from the callingsubscriber, and is informed. .that a subscribers line B, whichterminates at a distant machine switching ex change is desired,whereupon she tests for an idle; trunk leading to -the machineswitching,

exchange in thewell known manner. I Assumingthei central oflice trunk Mt0.'be' the first idle :trunk encountered, the attendant inserts plug220into jack 400 and actuates the dial 348..in accordance with the numberof the desiredl-ine..

lVhenplug 220 is inserted in jack 400 of thewoentralfoltice trunk M,relays 202. and

402 operate in a circuit extending from bat-.

tery, winding.- of relay; 402, contacts 401: of jack z400,..sleeve;contacts ofjack 400-and lug 220,1Winding of .relay202 to.ground. Relay.402.locksz.to the-sleeve of jack 400, "and at its two ,right han'd.armatures, connects ground and battery, respectively, to the .two

platesot condense1n405 by way of. theIrighthand winding of. relay. 403.:Batteryis connectecl to the condenser 405: bywayof both. the-left-handwinding of relayl403 and lamp 404, neither; of which, I however, are Ienergized since there is no complete direct current-.patln established.The charge on the.

condenser at this timeis foria purpose hereinafter to hesetforth.

Relay 202, at-.its' armature 221, removes thescontrolaof.lamp 208 fromthe calling supervisory relay 209 andcauses it to be extinguished. Atitsarmatures 223 and. 222,

it .disconnectsthe battery. .and ground, through -thewinding.of-retardamon coil 203, which, originally supplied the callingpartywitlrtalkingbattery. The operation of .relay. 202-does, however,not cause the release of. answering supervisory, relay 201 whichtis nowheld operated in a circuit extending; fromngrounded battery 415,2 windmg.o-f relay; 406, back. contact and .mner. armatureof relay 407, contact409 of jack 400, ring contacts of-jack 400 andplug 220, lowennon:malcontacts of key -229,'contacts1218. of re-.= lay 212, conductor 254,upper; outer armature andback contact of relay 352, conduc--.

tor 342, upper,normalcontacts 0f-Telay:335 ,.5

conductor 234, front contact andarmature. 216 of relay, 212,contacts-"2270f. key 210,

winding, of (calling supervisory relay 209,

contacts 250 of key 210, winding of answer.-

ingzSu-pervisory relay 201, lower, normal contactsof key 205, ringcontacts ofaplugn 200 and jackJ and thence over the establlshed,connection including line A, back to: the tip contacts of jack J andplug 200, "up-- .per normalcontacts of key 205, armature 215 and .frontcontact of relay 212, conductor 233, lower normal contacts of relay 335,conductor 337 back contact and. outer lower armature of relay 352,conductorv 253, contacts 217 of relay. 212, upper. normal contacts -of.key 229, tip contacts of plug 220 and Jack. 400,. to ground overtheback contact and outer armature of. relay-407. Re'-- I lays 209 and 406also operate inthis circuit 208' hasalready been extinguished by theoperation ofrelay 202. -Atits armature 225,

relay. 202 connects the ring conductorof the rear end of. the cord Ktothe contacts 227 of key. 210. In attracting its armature 226, relay 202causes/relay 207 to operate in a clrcuit extending from groundedbattery, over the armature226 andlirontcontact of relay. 202, 'winding.of relay. 207,-i1'rontcontact-and armature-of relay201, and thence togroundon the'sleeve circuit.

Relay 207, in attracting. its armature 260, connects the two upperwindings of retarda- .tion coil 203 to the normal contacts 227 and 228of key .210, and at its armature 261 short circuits relay 209, causingit' to release.

coil 351 is connected across the front end of theucord circuit and itwill also benoted that. atthis .timethe tWo upper windings of retardcoil 203 and the subscribers substation-set are connected in parallelwith retard coil-1351. I the circuit hereinbefore traced, causes the lowresistance Winding of relay 407 to be energized, whereupon the lineswitch plunger 450 is actuated to connect the trunk conductors to theterminals of the selector switch S.

Dialing.

.As' hereinbefore described,-the' retardation Relay 406, operating inThe attendantnow operates the-dial 348 v.to select the number wanted bythecalling subscriberzat A and when the=dial 348 leaves normal positionthe slow releasing relay 339 I operates-in an obvious circuit, Inattract ing its tworight-hand armatures, relay 339 disconnectstheoperators telephonesetfrom the. rear end-of cord:c ircuit, and -at itsleft-- hand armature, causes rela; 350 to operate Relay 209 performs nofunction since lamp in an obvious circuit. Relay 350, at its lowerarmature, disconnects the retardation coil 351 from the front end of thecord cir cuit, and substitutes the dial contacts of dial 348 therefor.At its upper arn'iature, it causes relay 335 to operate in a circuitwhich may be traced from grounded battery. through the winding of relay335, over the trout contact and upper armature of relay 350, contacts391 of relay to ground over the front contact and upper armature of relay 325.

Relay 33.3, in operating. locks itself in the circuit just traced,independent of relay it its two outer armatures. relay 33-5 supplies thecalling subscriber with talking battery ver a path. extending frombattery, contacts 3 2 of relay 30- resistance. clen'ient 2364i, lowerlei t-hand winding of repeating coil n05, lower armature and front contaot relay 335, conductor 233. front contact and armature 215 of relay212, upper normal contacts 0t key 205. tip ot plug 200. thence out overthe established connection and back to the ring contact phi a 200. lowernormal contact 0? key 205, winding of supervisory ay 201, contacts 250oi lzey 210, outer left hand armature 261 and contacts o'l relay 207.contact 227 of key 210 armature 210 and troutcontact o't' relay 212,conductor 23 1-, upper armature and trout contact of relay S515, upperletthaud winding of repeating coil 305,

resistance elementi-ltt to ground over the contacts 308 of relay 303. Itis now apparent that relay 201 remains energized at all times, beingsupplied with battery, 'lirst from the cord circuit K, then from theline switch connected to trunlr hi, and linally from repeating coil 365in the attendauts dialing circuit. l-ly this arrange ment the subscribermay flash the attendant at any time durinr the connection.

The attendant in operating the dial in accordance with the desirednumber actuates the selector S and connector C in the well known mannerto conne t the conductors o'l trunk to the terminals of the desired lineB and need not be described in detail. It will be understood as wasstated in connection with relay 100 that relay G maintains the lineswitch plunger 450 operated during the interval between the energizationot the right-haniil winding of relay 4-07 and the seizure of an idleselector switch 5%. and that when the connector C is seized a ground onterminal H0 thercot holds relay 4-07 operated.

When the connector C reaches the called line B, and the same is idle,ringing current will be connected to the subscriber s line in the wellknown manner, to signal the called subscriber. When the called subscriber responds to this signal, and removes the receiver from theswitchhook, back bridge relay s ll operates, causing the reversal ofbattery over the established conection in the well known manner. Thisreversal does not al'l'ect relay -l0 at this time since its right-handwinding is disconnected from t e trunl-z M at the back contacts of relaylt, r completing the dialing operai} i q lzty lthe rclay 339 will haverestored when the dial returns to normal, so that me circuit for relay350 is opened, whereupon this relay releases. Relay 335, howere', isheld operated over its locking circuit to ground on the front contactand upper arn ure of relay 325. The left-hand windin s ot' the repeatingcoil are then bridgeu across the tip and ring conductors of the rear endof the cord circuit by way or" the arniatures and front contacts of reay335, conductors 233 and 234 and the front contacts and arinatures 215and 210 of relay The secondary winding of repeating coil is connected inparallel with coil 351 and with the two upper windings of retart ationcoil 203, and is connected to the front end of the cord by way of theoutermost armatures and back contacts of relay 352, conductors 253 and254-, contacts 217 and 218 ot' relay 212, to the front end of the cordcircuit K. The calling subscriber may therefore now converse with thecentral ollice. subscriber at station B through the attendant stelephone and dial circuit. However, should the attendant restore key 20i, relay 2J2 releases. removing ground 'l rom the upper winding 01 relay21.2 in series with relay 32:), whereupon these relays release, thecircuit for the lower winding 0t relay 212 being open at the contact 211of key 204. Relay 212, in releasing, disconnects the attendantstelephone and dial equipment from the cord circuit so that the wallingand called subscribers may converse directly through the cord circuitwhich un der this condition is bridged only by the two upper windings ofretardation coil 203.

At the termination or" the conversation, the calling subscriber replacesthe receiver on the switchhook, thereby opening the circuit 'l oranswering supervisory relay 201 which, in releasing, causes lamp 200 toilluminate over an obvious sleeve circuit. This signal serves as adisconnect signal to the private branch exchange attendant, whereuponshe proceeds to take down the connection.

Removal of plug 200 from jack J opens the sleeve circuit, therebycausing lamp 206 to be extinguished. 'vVhen relay 201 releases, thecircuit for relay 207 is open, whereupon this relay restoresdisconnecting the middle high resistance winding of re- 1 switchterminals.

1 60! indicated by the arrow;

in such a manner" that, when current is fiowtardation ooil 203 from thecord circuit. COlltttCt, so that "tard-coil fronra'cross' the cordc'ircuit'is for the purpose o-f holding the central ofiice switches'opei 'ated after the calling subscriber replaces hisreceiver and mm the"attendant removes the v plug' 220 from jack VV'hen' the ca/lled"subscribenat station B replaces the' receiver on the switchhook, re-

, lay 411"releases?restoring the original battery andgrou'ncbconnectionsto the selector i The Withdrawal of plug 220' fronrjack aoo: alsoreleases relays'202 and 402. l he' i 'eleas'e of relay 202-restores 1the cord?circnit equipment to normal condition.

= Relay '402, on"restoring, reconnects the 1 bridge including thecondenser 405 and the' right hand"winding-30f relay 403 to the tip andring conductors of* the central "office- 1 trnnli M. JL'iSt prIOr-tothe'release 'of'relay 5 402;the upper plate;-of condenser 405' wasconnected to i the 3 negative :13 olesof A battery I 4 12 and 413;-wh'ereas t'he ylow'er' plate" was connected to the positive poleorground, so thatthe-condenser was charged to'the po- 40 tential of thisbattery'which, in systems of thi's type, is about 48 Volts. VVithrelay411 *releasech it will be noted that the negative 1 pole of the battery416 associated'with the i winding of relay 414 is connected to the ring*side bf the co'n'nectioir and thence-through the ri ght hand Winding"'ofrelay '403 to the lower plate' ofcondenser 405, whereas thepositivepolei or' ground is'connected to the tip side of't he'connectionand then'ce to the' 0 upper plate of this condenser. This condi- 1 tion'of battery and ground is'ijust the "re verse 0f that existingwhen'"relay 402 was o oei 'ated,so that there will be a potentia'l of a out 96volts (assumingthe centraldoflice battery and the local privatebranch'exchange battery t'o'be of the same voltage-was will' 'ordinarilybe'thecase) across the right hand wind 1? ing ofrel-ay 403, whichwill'cause' a current flow through this winding in thedirection Relay403 is -poled i HQ iH the direction indicatedflthe flux set up in theright hand Wi11'Cl iI1g"Will iQIOPOSG i i that set up by the: left hand:Winding when fore, will' not therefore, apparent that the differentialcfits circnit is closed through its own front the following action takesplace: Due'to thecurrent flow in-the right hand Winding: of relay 403,this relay will operate andclose its contacts, thereby coinpleting thelocking circuit through its left hand Wind ng. soon as this locking C11-cuit is=conrp'leted;'the'flux set up in the left hand winding willoppose that setup :by

the right 'hand' winding, whereuponthe re- Y lay rele'ase's. Ihis'actionwill repeat itself until the "eharge on thecondenser *405has been:reversedf'so th'at the relay"403 will cause its armature tovibrate.This differential effectof-"relay i'403, thereforapre vents'-'th1s relayfrom pern'ianently *closing its locking circult and causing theilhuni-*--nation-' of l amp 404 as a false indication of an 'inconiingrcall. iThecondenser- 405 is now fully charged from the connector battery 416'and when the selector switch S releasesyitgcauses thevnegative pole ofthe line switch battery 4'15 to'be connected to the ring conductor ofthe'trunk and ground to that-1p. TlilS'CliiI'lQBl) is'therefore -in thesame direction? as the current from the 'connector battery 416 sothatthere is no reversal ofcurrent tocause any change in the charging 0f:the condenser 405 so that there will be no current flowthrough theright hand winding iof relay 403. The lamp 404, there be falselyoperated. Itis,

fectof relay 403 provides" an arrangement whereby'the "releaseyof the'autoniatlc switches at the central office does not cause falseoperation of the signaling device 404.

Should the operator remove plug I 220 from jack 400 before the calledsubscriber at Bhangs up the' IGCGlIElfdC-lfijf4611 will still be'ioperated so that the nea'ative-pole of battery 416 is connected to thctip conductor 0f the connection'instead of to=the ringas in thepreceding case, While ground is connected tethering"instead of the tip.This is the condition w hiclrwill be met by the right hancl arm'aturesofrelay 402' when 'they restore and: since this is the same condi-:in'the' right "hand Winding 'of relay 403 and "consequently. nocfalsesignal given. The prel'ini'inary l charge on condenser 1 405 I thereforeprevents false operation of lamp 404 inrthis case. i r r V I Thesubscriber,'having hung up thereeeiver and "the :selectors having beenreleased-, the negative pole 0f battery \415rwill' be connect- "ed tothe:ringconductor of therconneetion tial effect of relay 403 thenprevents the per manent closure of its locking circuit to cause thefalse operation of lamp 404.

Connection from U. 0. to P. I). X.

The trunk M is arranged for two-way operation, its central oi'tice endhaving multiple connector terminals shown at D. On a call incoming tothe private branch exchange from a central office subscriber, thesubscriber actuates the dial associated with his station in order toconnect the calling line to the connector terminals D in the well knownmanner. then the trunk M is seized ringing current will beautoi'natically connected thereto to cause the operation of relay 403through its right hand winding. Relay 403 in operating locks up andestablishes a circuit for lamp 4:04 by way of the contacts 417 of jack400. The illumination of lamp 404 indicates to the private branchexchange attendant that a call is awaiting her attention. She thereuponinserts plug 220 of her cord K into jack 400 of the trunk M and,

actuates the key 204 in order to connect her headset to the cord andproceeds to set up the desired connection. The arrangement hereinbeforedescribed in connection with the release of the automatic switches on anoutgoing call functions in a similar manner on the release of theautomatic switches on an incoming call and it is believed unnecessary torepeat the action of relay 03 and condenser 405 under this connection.

Connection from P. B. X. to 0. 0. (P. B. X. subscriber dialing).

Should the calling party at A desire a central oflice connection andwish to dial the called subscriber himself, he proceeds in the samemanner as hereinbe'lore described in signaling the P. B. X. attendant,who then actuates her listening key 20% to place her headset across thetip and ring conductors ot the calling line. The calling party thenrequests a through dialing connection. Upon receipt of such a request,the P. B. X. attendant extends the call to an idle central officetrunkby way of plug 220 as in the preceding description, operates thethrough dialing key 210 and restores the listening key 204:. Theinsertion of plug 220 into the jack 400 of the central ofiice trunkcauses relays 202 and 207 to operate as hereinbe fore described so thatwhen the through dialing key 210 is operated, contacts 250 and 228 areopened to cut of? the retardation coil 203 from across the tip and ringof the cord. Contacts 21.9 of key 210 are closed, thereby cuttingthrough the ring conductor of the cord. The function of key 210 is,therefore, to place the calling subscribers line directly across thecentral office trunk so that the subscriber is in a position to dial thecentral office direct. On such a connection, when the calling and calledsubscribers hang up the receivers, the central oiiice auto- .maticswitches are automatically released,

Connection from one P. B. X. to another one?" a tie line.

In many instances a local P. B. X. subscriber desires to communicatewith another subscriber whose line terminates in another 1. B. X. Inorder to set up such a connection it is necessary for the P. B. X.attendant to employ what is known as a tie line which interconnects thetwo P. B. X.s.

When such a call originates at a local subscribers station, theattendant answers in the'usual 111a uner by inserting the rear cord plug200 into the jack of the calling line such as jack J and actuates hertalk and dial key 204 in order to connect her headset to the callingline and learn the nature of the desired connection. Upon learning thata subscriber whose line terminates at another P. B. X. is desired, theattendant tests for an idle tie line leading to the desired P. B. X. andon finding one she inserts plug 220 of the front end of her cord intojack 500 of the idle tie line. The actuation of key 204 performs thesame functions as described in the previous connections and need not berepeated here.

When plug 220 is inserted into jack 500 a circuit is established forrelay 501 over the local jack contacts. In attracting its armatures 520and 521. relay 501 short circuits condensers 530 and 531 and connectsthe pulsing relay 50a to the "front contacts of relay 508. At itsarn'iatnre 522 it causes relay 505 to operate in an obvious circuit,which in turn causes relay 506 to energize and connect ground to thesleeve oi jack 500 through the winding of relay 507. Relay 506 inoperating causes relays 510 and 508 to operate in a circuit extendingfrom battery, through the winding of relay 510, right hand armature andback contact of relay 509, conductor 511, winding of relay 508, armatureand front contact of relay 506 to ground. Relay 510 locks up independent of relay 509, whereas relay 508 connects the tip and ringconductors of the front end of the cord circuit to the pulsing relay504. The attendant then actuates the dial 348 in accordance with thedigit or digits to be dialed, whereupon the connection is established inthe well known manner.

The attendant receives supervision on lamp 206 from her local P. B. X.subscriber in" the=sanie inanner as described in the precedingconnections and upon receipt of a disconnect signal at the-terminationof the connection 'she Withdraws plug 220 from jack 500 causing all therelays, operated, to release. In this connection it will be noted thatrelays 202, Tand 507 do not operate. The calling subscriber therefore;receives talking batteryfrom battery associated with armature 223 ofrelay 202.

i into the jack 400, in such a case it is necessary that the attendant scord circuit be capable of completing the connection over the tie lineby permitting her to dial. over the rear cord.

Assuming that the P. B. attendant has received a request from a centralofiiceoporator to complete a connection to another ,P. BI XL, she testsfor an idle tie line in the Well known a manner, and findingjone sheinserts plug 200 of her cord into jack 5000f the tie line and actuatesthe through dialing key 210. It is assumed that the attendant has heldthe talk and dial key :204 actuated. The inse'rtion 1 erplug 200 intojack 500 causes relay 501 to operate in acircuit extending from battery,WiilClllig Of relay 501,:condu'ctor 502, local contact and spring ofjack 500 to gr'ound. .Belay, 501in attracting its arinatures ,520 and521 short circuitsflthe condensers 530 and 531 and connects the pulsingrelay 504 to the front contacts of relay 508. In-at tracting itsarmature 522, relay 501 establishesan obvious circuit for-relay505-,Wh'ich in operating establishes an'obvious energizing circuit-r forrelay 506.' Atrits armature 523 relajy;501 causes relay 509 to operateina circuit extending from battery,- lamp 20.6, back contact andarmatureof .relay- 201, sleeve contacts of plug 200 and jack 500, armature 523;and front contact of relay 501, right-hand winding of relay 509,Iarmature 522 and front contact of relay 501-130 ground. Belay 506 .inoperating connects ground to the sleeve contact of jack 500, by Way ofthe winding of relay 507, which. relay, op crates in the sleeve circuitjust traced, to around over the armature and front contact io f relay506. Relay 507, in operating, connects the ground on the lowerarmatureand baclccontact of relay 508, to the Winding of relay. 510- which.theneupon operates and V connects thesame groundwhich effected its,operation, to theupperterminal of relay 5 "508 so that relay 508doesnot operate, since The operation of relay 508 take placeimmediatelyfollowing the opits lower terminal is also connected toground at the armature and front contact of relay 506. Lamp 206 isilluminated'in the circuit previously traced for relay 507.

' lVhen keys 204 and 210' are actuated-a circuit is established forrelay 363 extending from battery winding of relay 363, conductor280;lowermost alternate contacts of key 204, conductor 281, contacts 282of .liey 210,; conductor 283 back contact and armature of relay"'201,"sleeve contacts 'of plug 200 and jack 500, winding of relay 507,to ground over the armature and front contact of relay 6. Relays 212 and213 also operate as a consequence of theactuation of key 204 (asdescribed hereinbefore), so that With the added'operation of relay 363,due

'to the actuation of both keys 204-and 210,

the lefthand windings of repeating-coil 365 and resistance element 364arebridged across the front end of the cold by "Way of the uppermost andlowermost armatures and front contacts of relay 363, conductors 253 and254, and the make-beforeJ-break contacts 217'and 218 of *relay 212.Tli-is bridge acts as a holding bridge for the central oilic'e switches.In attracting its inner upper armature, relay363 establishes air-0b-VlOUS circuit for relay 352; Relay 352 operates and at its outermostarmatures and back contacts removes the bridge: including theretardation coil 351from across thetip and ring conductor of the'frontend of the cord. The coil 351, however, 'is noW bridged across the rearendof the cord. f

It will-be noted that when relay 352 op erated, the circuit for relay363 was transferred from the ground on the armature and front contact ofrelay 506 by way of the Winding of relay 507, to the ground on theuppermost alternate contact ,of jke'yf2l0. This new circuit may betraced I from grounded battery, Winding of relay 363,- inner upperarmature and front contactof relay352, conductor 295, contact 260 -ofkey 204, groundfover the contacts 261 of key 210. The effect ofthis'transfer isto shunt out relay-507 which on releasing permits relay508 to energize in a clr'cuit extending from grounded battery, windingof relay 510, front contact and jarmature of relay 510, Winding of relay508 .to ground over the armature and front contact of relay, 506. "Willtherefore eration of relays 352 and 363 so that relay 504 is not outthrouohto' receive the dial impulses until'relays 352' and 363 haveoperated to. cut on? the central ofiice'battery. The reason for delayingthe connection'of the pulsing relay 504 to the rear end tor dialing endin this case) of the ,cordK is to prevent this relay from responding tothe central ofiice battery ,and thereby effecting a false connection.

In order to dial over the rear end of the cord on a connection trom acentral office to another I. B. X. it is therefore necessary first, tosupply the central otlice switches with a holding bridge; this isaccomplished by the actuation oi relay 363 which connects the left handwindings of repeating coil 365 and resistance element 36% across thefront end of the cord circuit. Second, the pulsing relay of the tie linemust not be connected to the rear end of the cord until central otlicebattery is disconnected from the front end of the cord; this isaccon'iplished by the peculiar relay arrangement associated withapplicants tie line and by the operations of relays 352 and 363.

The attendant now operates thedial 348 in accordance with the desirednumber and as it is moved from normal position relays 339 and 350 areenergized as in the previous case. Relay 335, however, does not operateas its energizing circuit is opened at the lowermost armature and backcontact of relay The operation of relay 350 places the dialing contactsdirectly across the conductors 233 and 234 by way of the normalmakebetorc-break contacts of relay the conductors 233 and 234 beingconnected to the tip and ring conductors of the rear end of the cord byway of the front contacts and outer upper and lower armatures of relay212. The interruptions of the dial contacts as the dial restores tonormal cause the intermittent operation of pulsing relay 504, therebysetting the automatic switches 'in the well-known manner to effect thede sired connection. It is believed unnecessary to trace the connectionany further or to describe the disconnect operations since these arequite obvious in View of the preceding descriptions.

What is claimed is:

1. In a telephone system, a plurality of cord circuits, a dialingcircuit common to said cord circuits, an operators telephone set, a keyfor each of said cord circuits, a relay controlled by one of said keysfor connecting said set and said dialing circuit to a corresponding cordcircuit, and means controlled by the operation of said relay forrendering a corresponding relay i another of said cord circuitsinoperative to connect said set and said dialing circuit with another ofsaid cord circuits.

2. In a telephone system, a plurality of cord circuits, a key for eachof said cord circuits, dialing equipment common to said cord circuits, arelay in each of said cord circuits normally responsive to the actuationof a corresponding cord key, a relay in said dialing equipment, andmeans responsive to the actuation of one of said keys for operating therelay associated with the dialing equipment, thereby rendering the actuation of a key in another cord circuit ineffective to operate itscorresponding cord relay.

3. In a telephone system, a plurality of cord circuits, dialingequipment common to said cord circuits, a key for each of said cordcircuits, a bridge circuit associated with said dialing equipnient, arelay for each of said cord circuits responsive to the actuation of oneof said cord keys for connecting said bridge with a corresponding cordcircuit, and means controlled by said relay for rendering the operationof a second cord key inetfective to connect said bridge with a secondcord circuit.

4. In a telephone system, a cord circuit having a front and a rear end,dialing equip ment, a dial key associated with said cord circuit andadapted upon actuation to connect said dialing equipment to the frontend of said cord, a second key, and means responsive to the jointoperation of said keysfor associating said dialing equipment with therear end of said cord.

5. In a telephone system, a cord circuit having front and rear ends,dialing equipment, a repeating coil, a key in said cord circuit normallyoperative to connect said dialing equipment to the front end of saidcord, a second key, and means responsive to the operation of said firstand second keys for connecting said dialing equipment to the rear end ofsaid cord and a bridge including said repeating coil to the front end ofsaid cord.

6. In a telephone system, a telephone exchange, a machine switchingexchange, means at said telephone exchange including a trunk circuit anda plurality of automatic switches for establishing a connection throughsaid machine switching exchange, a signaling device, and meansassociated with said trunk circuit for rendering said signaling deviceinoperative upon the release of said automatic switches when said connection is terminated.

7. In a telephone system, a telephone exchange, a machine switchingexchange, means at said telephone exchange i neluding a trunk circuitand a plurality of automatic switches for establishing a connectionthrough said machine switching exchange, a signaling device, and abridge circuit associated with said trunk circuit for rendering thesurges caused by the release of said automatic switches at thetermination of said connection, ineffective in actuating said signalingdevice.

8. In a telephone system, a trunk circuit having an alternating currentbridge circuit normally connected thereto, said trunk adapted tofunction with automatic switches in the establishment of a telephoneconnection, a double wound relay in said bridge circuit, one of saidwindings adapted to maintain said relay operated after its other windinghas been energized by alternating current incoming over said trunk, andboth of said windings being so related as to prevent said relay frombeing permanentlyoperated whensaid other Winding is energized byelectrical surges caused by the release of the aforementioned switchesat the termination of a connection.

9. In a telephone system, a telephone exchange, a machine switchingexchange, means at said telephone exchange including a trunk circuit anda plurality of automatic switchesforestablishinga connection throughsaid machine switching exchange, an alter nating current relay normallyconnected across said trunk'circuit and disconnected therefrom when saidtrunk is seized in establishing a connection through said machineswitching exchange, means responsive to the release of said automaticswitches at the termination of said connection for reversing currentover said trunk, said alternating current relay being subjected to saidcurrent reversal, and means including a secondary winding on said relayfor rendering said relay unresponsive to the currentproduced by saidreversal.

10. In a telephone system, a central office exchange, automatic switchestherein, a second exchange, a tie line terminating therein and leadingto a third exchange, a pulsing relay associated with said tie line,means at said second exchange for extending a connection from said firstexchange to said third exchange, said connection including saidautomatic switches and said tie line, and means at said second exchangefor delaying the connection of said pulsing relay to said tie line untilthe central office battery associated with the established connection isdisconnected therefrom.

11. In a telephone system, a central oflice exchange, automatic switchestherein, a second exchange, a tie line terminating therein and leadingto a third exchange, a pulsing relay associated with said tie line,means at said second exchange for extending a connection from said firstexchange to said third exchange, said connection including saidautomatic switches and said tie line, a dial, andmeans at said secondexchange for supplying a holding bridge for said central office switchesand for thereafter connecting the pulsing relay of said tie line to saiddial.

12. In a telephone system, a telephone exchange, a tie line terminatingtherein, a puls ing relay associated with said tie line, an o-peratorscord circuit having front and rear ends, a dial, a key in said cordcircuit for connecting a bridge across said cord circuit, a second key,means responsive to the joint op-f eration of said keys for connecting abridge across the front end of said cord, and thereafter connecting saiddial to the pulsing relay of said tie line, and means responsive to theactuation of said dial for disconnecting said first mentioned bridgefrom said cord circuit. V w

18. In a telephone system, a telephone. exchange, a normallydiscontinuous tie line terminating therein, an operators cord circuit,dialing equipment, a relay in said tie line, means responsive to theconnection of said cord circuit with said tie line for connecting ashunt about said relay, and key controlled means for connecting a bridgeacross one end of said cord circuit and there after removing the shuntfrom said relay, whereby said relay operates to render said tie linecontinuous.

14;. In a telephone system, a telephone exchange, a tie line outgoingfrom said exchange, a cord circuit having a plurality of keys, dialingequipment, means responsive to the actuation of one of said keys forassociating said dialing equipment with the front end of said cord whensaid front end is connected to said tie line, and means responsive tothe joint operation of said keys for associating said dialing equipmentwith the rear end of said cord when said rear end is connected to saidtie line.

15. In a telephone system, a telephone exchange, a second exchange, atie line interconnecting said exchanges, a cord circuit having front andrear ends, a key in said cord circuit, dialing equipment, and meansresponsive to the actuation of said key for as sociating said dialingequipment with the front end of said cord whereby a connection may be,extended from said first exchange through said second exchange by way ofsaid tie line.

In witness whereof, I hereunto subscribe my name this 23rd day ofOctober A. D., 1923.

WALTER P. ALBERT.

